Performance Expectations for Reduced-Size Antennas

Every device that transmits and/or receives radio signals needs an antenna. When that device has a small size or limited space for a classic resonant antenna, various techniques are used to implement reducedsize antennas. Those techniques may include inductive or capacitive loading, meandered or spiral construction, high dielectric constant materials to slow down wave propagation, and embedded structures incorporated into the packaging. Each of these methods imposes some type of limitation when compared to monopole, dipole, or resonant loop antennas. This tutorial looks at the key limitations of small antennas, with the intention of illustrating what level of performance can be expected from the various design options.